Acute Flaccid Myelitis in the US

As of October 23, the CDC has confirmed 62 cases of acute flaccid myelitis (AFM) across 22 states in the US. These confirmed cases are among 155 reports of patients that are under investigation for this syndrome. This current increase in AFM cases is following a pattern similar to two previous increases in 2014 and 2016: an increase in cases starting in late summer/early fall and disproportionately affected children. Health officials have yet to determine the cause of this syndrome, which is now being widely reported across national media channels.

In this week’s post, we take a closer look at AFM, including potential etiologic agents and the challenges of communicating about a rise in cases of a worrisome condition, for which much remains unknown.

A Closer Look at Acute Flaccid Myelitis

Acute flaccid myelitis is inflammation of the spinal cord, which limits the ability of the brain to transmit signals to muscles throughout the body. Symptoms include reduced control the arms or legs and decreased function of facial muscles and reflexes. The most life-threatening complication of AFM is respiratory failure due to decreased function of the muscles responsible for breathing. Since 2014, the CDC has reported 386 cases of AFM, 90% of which have affected persons under age 19, with an average age around 4 years.

There are a range of hypotheses about the potential causes of AFM, including viruses, toxins, and genetic conditions. However, diagnosis is difficult because AFM presents with symptoms similar to other neurological diseases, including Guillain-Barré syndrome. Additionally, potential causative agents have not been consistently identified by clinical or laboratory testing, posing a challenge for public health response operations. There are no commonly practiced treatments for AFM patients, and there is limited research on the long-term effects of the disease.

Looking for a Source

One pathogen that has shown a potential link to AFM during a previous rise in AFM cases is enterovirus D68 (EV-D68). In the fall of 2014, the CDC confirmed 1,153 cases of EV-D68 across 49 states. The 2014 AFM and EV-D68 outbreaks occurred concurrently, prompting suspicion of a possible relationship. The thought was that EV-D68, a disease that most commonly presents as a respiratory condition, had managed to induce neurological symptoms in a fraction of its patients. In addition to the coinciding nature of the EV-D68 outbreak and a rise in reported AFM cases, this suspicion derived from the fact that other enteroviruses had spawned cases of AFM in the past.

While multiple studieshave identified a potential link between EV-D68 and AFM, none have definitively demonstrated a causative relationship. The CDC notes that the 2014 EV-D68 outbreak coincided with the rise in AFM cases, but they were unable to “consistently detect EV-D68 infection in every [AFM] patient.” Additionally, the CDC has tested AFM patient specimens for “a wide range of pathogens,” including EV-D68, but none have been “consistently detected in the patients’ spinal fluid,” a likely location for the causative pathogen considering that AFM directly affects the spinal cord.

After the coincident EV-D68 and AFM cases in 2014, the CDC has closely monitored for EV-D68 during increase in AFM cases. During 2015, a year with fewer AFM cases, the CDC saw very small numbers of EV-D68, and the CDC only saw clusters of the suspected virus in 2016—during the largest number of recorded AFM cases in recent years (149 cases). The CDC is currently seeing another spike in AFM cases, but there are no reports at this time of a concurrent increase in EV-D68 infections. This reality moves public health professionals back in to a realm of uncertainty, a position that limits public health response options.

Communicating AFM: Managing Uncertainty

On October 17, CDC officials held a telebriefing to address the current rise in AFM cases. During this conversation, CDC representatives frequently addressed the unknowns of this increase in cases and stressed two important messages about AFM: that the disease is rare and that it is serious. These messages were tied with additional statements that encouraged avenues for action and pledged transparency from the agency as response to the situation continued.

Open and clear communication during the response is a critical tool to mitigating public concern. This is particularly true since the disease is rare, can have long-lasting impacts, and the cause remains unknown. Currently, these factors are grabbing the attention of national media outlets, compounding the fear associated with AFM. The rarity and severity of AFM has increased its reporting, and the unfortunate adjective “polio-like” has become common vernacular across news outlets. When paired with heart-wrenching stories of AFM victims, the uncertainty makes it is difficult for members of the public not to fear this rare and mysterious disease.

Although there are no public records of health officials requesting that media outlets refrain from using the term “polio-like” in their AFM coverage, there is an noticeable absence of this term from CDC communications. In addition to this absence, the CDC representatives leading the aforementioned telebriefing made a point to explicitly mention that every AFM case had tested negative for polio. This statement was clearly designed to emphasize to the attending media representatives that polio was not the cause of the reported AFM cases. In practice, removing polio as a potential cause should reduce public concern, but there are reasons to expect that the widespread use of terms like “polio-like” in press coverage may dull this effect. One can argue that AFM coverage utilizing the term provides an accurate description of disease symptoms but muddles the information surrounding the disease’s source, introducing an opportunity for misinterpretation. Despite using the suffix “like,” this widespread use of a potentially misleading adjective could increase public risk perception and build incorrect associations amongst members of the public.

Typically, responding health agencies could counter these concerns with correct information about the cause and nature of the AFM cases. In the case of AFM, however, the surrounding uncertainty severely hampers health officials’ collective ability to counter potentially misleading information. Sharing information to a concerned public provides opportunities to promote protective behaviors aimed at reducing both risk and concern, but in the case of the AFM, uncertainty at each level presents a challenge that limits the most effective response activities, frustrating scientists and stoking concern amongst the public. Currently, CDC officials have resigned to limiting communication about both prevention and treatment, suggesting broad public health measures like proper hand hygiene and adhering to recommended vaccination schedules as pathways to limit risk of exposure. And even these messages have been issued with caveats about their protective efficacy, notably that they may be ineffective in directly reducing the risk for AFM since the root cause has not yet been identified. Despite these apparent communication challenges, health official have done a laudable job presenting a consistent message that addresses uncertainty, provides transparency, and promotes action to the extent possible under the circumstances.

Moving Forward and Lessons for Response to Future Outbreaks

Health agencies nationwide will continue to monitor and respond to this current rise in AFM cases. Public health officials will promote actions that mitigate known risks and search for the cause of this tragic condition, but there is no realistic timetable for answers. Without knowing AFM’s causative agent, there are serious limitations to the public health response, as it is impossible to specifically target root causes of the condition to effectively prevent or reduce transmission.

Looking forward, the contextual challenges shaping the information landscape during this rise in AFM cases could serve a proxy for future novel disease outbreaks. Uncertainty amongst public health professionals regarding emerging or novel pathogens would present similar challenges to risk communication and response activities as we are seeing with AFM. Challenges faced by the AFM response, effective solutions, and other lessons should inform best practices that could reduce the burden of similar outbreaks in the future.

Photo: Public education poster created by the CDC during the 2014 enterovirus D68 (EV-D68) outbreak. Photo courtesy of CDC.

Outbreak Observatory aims to collect information on challenges and solutions associated with outbreak response and share it broadly to allow others to learn from these experiences in order to improve global outbreak response capabilities.